1. Field of the Invention
This invention generally relates to a wheel examining apparatus for examining a wheel, in particular its alignment, such as the degree of inclination of a wheel, of a vehicle, such as an automobile, truck or trailer, and, in particular to a wheel examining apparatus for examining a wheel having a double wheel or double tire structure comprised of a pair of sub-wheels combined side-by-side for supporting a heavy load.
2. Description of the Prior Art
A wheel examining apparatus for examining the alignment or mounting condition of a wheel of an automobile, bus, truck, trailer or the like has been used. Various conditions are set in a wheel mounted on a vehicle and in particular the so-called inclination angles, such as toe angles, camber angles and caster angles are set in a wheel regarding its running performance. These inclination angles are examined once as one item of examination of a vehicle before the vehicle is shipped after manufacture, and they are also examined when a maintenance operation, such as exchange of wheels, is to be carried out for a vehicle after a period of use. In order for a vehicle to have an excellent running performance, it is important that these inclination angles be properly set and maintained. In addition, as a dynamic characteristic of a wheel, or a characteristic of a wheel while the wheel is in rotation, such parameters as wobbling of a wheel to the left and to the right and steered angle of a wheel are important. Since the running performance of a vehicle can be significantly affected by such a dynamic characteristic of wheels, it is quite important that the dynamic characteristic of a wheel can be measured at high accuracy. Moreover, there are those vehicles which use the so-called double wheel or double tire comprised of a pair of sub-wheels fixedly mounted side-by-side so as to increase the ability to support a heavier load. Since the stability of such a heavy duty vehicle is extremely important from the view point of safety in driving, it is also important that examination of such a double tire can be carried out properly and accurately.
Japanese Pat. Laid-open Pub. Nos. 51-83301 and 54-49701 disclose techniques for measuring the toe angle and/or camber angle of a wheel while the wheel is maintained in rotation. However, according to the teachings of these prior art techniques, although a wheel to be examined is supported on a pair of rollers to keep the wheels in rotation, either of the side surfaces of the wheel is not supported or a contact roller is brought into rolling contact with one side surface of the wheel to take measurements and the geometrical center of a wheel as an object to be measured is not located or determined by clamping the wheel from both sides, so that accurate measurements cannot be taken. On the other hand, Japanese Pat. Appln. Nos. 58-109235 and 59-9502 and Pat. Laid-open Pub. No. 61-41913 corresponding in content to U.S. Pat. No. 4,567,667 disclose techniques for locating or determining the geometrical center of a wheel supported on a floating table by clamping the wheel from both sides. However, according to these techniques, since the wheel supported on the floating table is static and non-rotating, there is no way to measure the dynamic characteristic of the wheel.
Japanese Pat. Laid-open Pub. No. 63-286742 corresponding to Japan Pat. Appln. No. 62-121128 and in content to U.S. Pat. No. 4,901,560 and U.S. Pat. No. 4,962,664 a divisional thereof, discloses a wheel examining apparatus capable of measuring the dynamic characteristic of a wheel while keeping the wheel in rotation under the condition of clamping the wheel from both sides. According to the teachings of this prior art reference, since a wheel is supported on a pair of rollers and the wheel is clamped by rollers at its opposite side surfaces, the dynamic measurement of a wheel can be carried out. However, the apparatus disclosed in this reference is suited mainly for examination of a wheel mounted on a four-wheel vehicle having two axles. Accordingly, the apparatus of the above-described prior art reference is not always satisfactory, in particular, for heavy load vehicles, such as larger-sized automobiles, trucks, buses and trailers, which normally have three or more axles and/or the so-called double wheel comprised of a pair of sub-wheels mounted side-by-side. For example, there are needs for improvements in a wheel guiding apparatus for guiding a wheel to a predetermined location of a wheel examining apparatus, improvements in examination of wheel alignment in a multi-axle vehicle having three or more axles, and improvements in accuracy in measuring the inclination angle of each of the component wheels in a double wheel system and in examination of a wheel of a vehicle suited for carrying heavy loads.